I. Field of the Invention
This invention pertains to the art of polymers, and more particularly, to polymer modifying agents for use in increasing the shelf life of rubber compounds.
II. Description of the Related Art
The short shelf life of uncured rubber has been a problem in the industry for quite some time. Oxygen and light activate the sulfur cure system and the accelerators in the rubber, causing premature curing, completely destroying the rubber. Different additives have been added to the virgin rubber to modify the properties of the rubber.
Mixing additives with virgin rubber is well known in the art. One known type is described in U.S. Pat. No. 5,650,454 to Hoover et al. Hoover et al disclose a rubber additive which increases tear resistance when added to a rubber compound. This compound comprises a cross-linked fatty acid, starch, and an asphalt carrier. One drawback of the Hoover patent is that the asphalt-based processes give a lower yield than the present invention, and the individual compounds are more toxic. A problem that is not addressed by the Hoover patent is the long-term storage of the tires. The current invention allows for an increased shelf life of the rubber. Another drawback of the Hoover patent is the length of time needed to process the compound.
Another known type of rubber additive is disclosed in U.S. Pat. No. 5,710,200 to Toratani et al. Toratani et al disclose natural rubber, containing viscosity stabilizers, treated with a strainer after compounding hydrazide stearate into the natural rubber. Storage hardening is purportedly suppressed and a decrease in molecular weight is prevented. One drawback of the Toratani patent is the toxicity of the hydrazide compound.
The present invention contemplates a new polymer-modifying agent for use in increasing the shelf life of uncured rubber, and for dispersing silica in the rubber compound. Thus, this invention is simple in design, effective in use, and overcomes the foregoing difficulties and others while providing better and more advantageous overall results.